1. Field of the Invention
The present invention relates to a computer-aided design system for use in plotting and drawing of figures and in other related editing work.
2. Description of the Background Art
Various systems known as computer-aided design (CAD) systems have been developed to support the plotting, drawing and editing of figures. These systems permit easy drawing and plotting of diverse figures and are capable of storing the results of such figure manipulation into a memory as CAD data. The stored CAD data may later be read out of memory for correction and other editing purposes.
In a CAD system setup, it may happen that CAD data on a plurality of separately plotted parts (e.g., engine, cover and frame of a motorcycle) are read from the memory and combined into CAD data constituting a single integral device (e.g., entire motorcycle) for display onto a CRT display unit. In that case, the CAD system must permit the operator to recognize clearances between the parts. The CAD data should then be corrected as needed. Otherwise the clearances between the parts may not be sufficient or one part may penetrate the other (a phenomenon called interference), thereby making the manufacture of the target device impossible. The avoid such interference, a conventional CAD system requires that the operator cut a number of cross sections out of the combined CAD data to check the value of clearance (hereinafter called the clearance value) for each cross section.
If the check on the cross sections for clearance values proves that any clearance value is insufficient or that some parts interfere with each other, it is necessary for the operator to manually correct relevant CAD data until all clearance values attain sufficient proportions. One disadvantage of the conventional CAD system is that the number of times a cross section is cut out is high and the process involved is inefficient. Another disadvantage is the inability of the system to check for the clearance value of any part of which a cross section is yet to be cut out. A further disadvantage is that an actual clearance value may not be calculated depending on the direction in which the cross section is cut out from the CAD data.
Furthermore, the process in which the conventional CAD system calls on the operator to manually correct relevant CAD data until sufficient clearance values are attained is tedious, time-consuming and inefficient. Inadvertent operations by the operator may bring the preparation of the CAD data to a premature end without sufficient clearance values being attained. In such a case, the insufficient clearance values are recognized only after manufacture of a prototype has begun.